Preliminary boiling or cooking process for cellulose



Patented May 23, 1933 KARL an; or nnnsmcrrons, rm'nann PRELIMINARYBQILING OR COOKING- PROCESS EQR, CELLUL OSE No Drawing. Gontinuatlon atapplication Serial Ito. 259,921, filed march 7, 1928, and in FinlandMarch 17, 1927. This application filed June 2? 1932. Serial No. 619,612.

- The present application is a continuation of my co-pending applicationSerial No. 259, 921, filed March 7, 1928, and relates to the productionof cellulose sulphite. More particularly, the present inventionrelatesto the provision of a shorter cooking period, a greater yieldofcellulose, and a lower loss of fibers in the waste lyes than is possibleaccording to any of the reviously known proc esses. At the same time,the quality of the cellulose is maintained substantially unimpaired, g

To the end of carrying out the invention, it is contemplated that thechips be impregnated either with gases, such for instance as ammoniagases, sulphurdioxide gas, nitrous acid gas, and acetic acid gas, orliquids containing acetic acid or salts such as acetates or phosphates,or a mixture of the acids and 21D salts, so that the resinous and fattymaterials are dissolved. This action taking place prior to the maincooking process. The liq-' uids employed for the preliminary treatmentdo not materially afiect the chips, being 25 adapted primarily fordissolving the resinous and fatty substances contained therein.

After such impregnation, the pro-cooking liquid is pressed into thepores of the chips in any desired manner, as by pneumatic, gas, or steampressure, and then cooked. During this pre-cooking treatment, theliquids, depending upon the kinds of wood undergoing treatment, areeither slightly alkaline, neutral, or slightly acid.

It is also possible for the impregnation to take place by pressure inthe absence of boiling, so that heat is used only during the subsequentor main cooking, in order to accelerate the main boiling ppocess.

After a thorough lmpregnation of the chips in the preliminary treatment,the pressure in the cooker is preferably returned to the atmosphericvalue, whereupon the chips, remaining in the cooker without subsequent 5washing, are filled up, dependent upon the type of cellulose to be made,with either alkaline or acid cooking-lyes, whereupon subsequent cookingtakes place.

When either the Mitscherlich or indirect process, or the Ritter-Kellneror direct cooking process, the two processes previously used incommercial practice, is employed, a working pressure of approximately 4:to 6 atmospheres, and a temperature ranging sary with the prior, directprocess. In addition, the yield of cellulose is increased toapproximately 48 to 52%, the loss of fibers in the waste lye is no morethan from 2 to 3%, and the tearing length varies between 8 and 9000meters.

With my process the novel advantage is obtained that if the boiling lyeemployed in the preliminary treatment is replenished by a quantity ofgas or liquid corresponding to that absorbed by the chips during theimpregnation treatment, this boiling lye can be employed several times,merely by circulation from one cooking to another.

llt is to be distinctly understood that it is desired to dissolve theresins and fats in the fibers in order that the fibers can then be linedwith the acetic acid, acetates, phosphates orother materials containedin the preliminary treatment. It is not sufiicient to place thistreating material in the ultimate or final bath, for then, the hydrogenor hydroxyl ions in the lye penetrate more rapidly than do the ions ofthe protective material, so that undesirable charring can not be avoidedat the elevated temperatures and pressures that I desire to'employ.

However, when the pre-treatment accordmg to my invention is employed,for example, with the addition of natron lye, phosphates, acetic acid,or acetates, then the temperature in the subsequent or main cookingtreatment, with for example, calcium-magnesium, or sodium-sulphite, maybe raised without danger to say 170 (1, while the pressure can beelevated to as high as 8 atmospheres. With such raise in thetemperatures and pressures, the cooking is greatly accelerated, withoutdeterioration of the quality of the cellulose,

an accomplishment unobtainable in the previous process, not employing mypreliminary treatment; and any attempt at such accelerated cooking wasalways accompanied by black boiling. One of the greatest advantages ofmy invention is that despite the raised temperatures and pressuresemployed, and consequent acceleration of the process, the quality of thecellulose nevertheless remains extremely high.

Especially when phosphates are employed in the pre-cooking, thispre-cooking material remains in the fibers to protect them during thehigh temperaturesmaintained in the main boiling process, it of coursebeing necessary to observe the precaution that the material undergoingtreatment is not washed between the preliminary and the main cookingprocesses.

Merely by way of example, the following three examples of my inventionare given.

Example 1 1000 kg of chips are impregnated for from 1 to 3 hours at atemperature above 100 C. and at a pressure of 4 to 8 atmospheres withsolutions of the acetates of calcium, magnesium, sodium or othercompositions which act in the same way and manner. The hot lye is thenintroduced into the next following cooker, which is filled anew, and thechips are impregnated in the same manner pointed out above. Theimpregnation is followed, without subsequent washing, by a main cookingwith bisulphite of calcium, sodium or magneslum.

' The cooking period in accordance with the direct rocess is 7 to 8hours, including the pre-coo mg.

Example 2 positions acting in a similar way or manner.

The hot lye is then introduced into the succeedmg cooker, and withoutsubsequent washs ing, an acid or alkaline cookingmethod fOlfi/ lows.

The process may also be carried out by introducting acetates andphosphates into the pores of the chips by means of gas, air, orhydraulic pressure, whereupon a slightly alkaline, neutral or acidcooking process follows.

Example 3 1000 kg chips are impregnated for 1 to 3 hours at atemperature above 100 C. and a pressure of 2-8 atmospheres with sodasolutions, which have been neutralized or made slightly acid by organicgases or liquids (for instance acetic acid or acetic acid gas) where'-upon a cooking with bisulphite of magnesium takes place, accomplished bymeans of comminuted magnesite, without subsequent washing.

It is of course obvious that the foregoing examples are by no meansexhaustive of the various possible ways of carrying my invention intopractice, and that numerous variations of the process, within the scopeof the invention, will readily occur to those skilled in the art uponperusal of my disclosure. Accordingly, it is contemplated that theinvention be limited only by the scope of the appended claims.

I claim:

1. The process comprising saturating cellulosic material with a liquidcontaining at least one substance selected from the group comprisingacetic acid, natron lye, acetates, and phosphates, and thenboiling thematerial without previous washing in'a bisulphite digesting liquor at atemperature materially higher than 130 C. and a pressure of materiallyhigher than 4 to 6 atmospheres.

2. The process comprising saturating cellulosic material with a liquidcontaining at least one substance selected from the group comprisingacetic acid, natron lye, acetates, and phosphates, and then boiling thematerial without previous washing in a bisulphite digesting liquor atatemperature 1n excess of 130 to 145 C. and pressure in excess of 4 to 6atmospheres, and not materially greater than 170 C. and a pressure ofapproximately 8 atmospheres.

3. The process comprising saturating ce1 lulosic material with a liquidcontaining at least one substance selected from the group comprisingacetic acid, natron lye, acetate, and phosphates, and then boiling thematerial without previous washing in a bisulphite digesting liquor at atemperature of approzimately 17 0 C. and a pressure of approximately 8atmospheres.

4. The process comprising saturating cellulosic material with a liquidcontaining acetic acid, and then boiling the material without previouswashing in a bisulphlte digesting liquor at a temperature ofapproximately 170 C. and a pressure of approximately 8 atmospheres.

5. The process comprising saturating cellulosic material with a liquidcontaining acetates, andthen boiling the material without previouswashing in a bisulphite digesting liquor at a temperature ofapproximately 170 C. and a pressure of approximately 8 atmospheres.

6. The process comprising saturating cel lulosic material with a liquidcontaining phosphates, and then boiling the material without previouswashing in a bisulphite dige'sting liquor at a temperature ofapproximately 170 C. and a pressure of approximately 8 atmospheres.

7. The process comprising saturating'celacetates and phosphates, andthen boiling the material without previous washing in a bisulphitedigesting liquor at a temperature of approximately 17 0 C. and apressure of aproximately 8 atmospheres.

8. The process comprising saturating cellulosic material with a liquidcontaining acetic acid and phosphates, and then boiling the materialwithout previous washing in a bisulphite digesting liquor at atemperature of approximately 17 0 C. and a pressure of approximately 8atmospheres. r

9. The process comprising saturating cellulosic material with aliquidcontaining acetic acid and acetates, and then boiling the materialwithout previous washing in a bisulphite digesting liquor at atemperature of approximately 170 G. and a pressure of approximately 8atmospheres. v

10. The process of preparing cellulose, comprising saturating cellulosicmaterial in. a liquid containing a mixture of substances selected fromthe group comprising acetic acid, acetates, natron lye, and phosphates,and then boiling the material without previous washing in a hisulphitedigesting liquor at a temperature of approximately 170 C. and a pressureof approximately 8 atmospheres.

11. The process of producing cellulose, comprising saturating.cellulosic material with a liquid containing phosphates, to dissolvethe resinous and fatty materials therein and to form a protective liningon the interior of the fibers, and then boiling the material, withoutprevious washing, in a loisulphite digesting liquor at temperatures andpressures materially in excess of those employed in the previously knownprocesses In testimony whereof I have signed my name to thisspecification KARL YRJU KYLANDER.

